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Thread: Test kits and accuracy

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    Test kits and accuracy

    Hey Guys,
    New to the forum and new to pools, I have had my pool for about four months now and have a few questions on test kits. My pool is in ground, white plaster, chlorine with Hayward AUTO chlorinator, cartridge filtration, sodium tetraborate add 3 months ago and Ozonator, I also have a 8 person spa, the total volume is around 16000 gals. My question is on the test kits and different ones that are available. It seems I am always off a little bit here or there on something, and want a more accurate way to measure stuff. The kit I have now looks similar to the ones mentioned, but it doesn't seem like the most accurate way to do buisness. Take a sample add a little of this and a little of that compare the color to a chart and gustamate it. I take a sample to the local pool store about once a month and noticed that their machine gives digital readings to the 10th place on everything. That is what I'm talking about! Are machines like these available to everyone? Do they cost more than my pool? Where would I get one? Just curiosity, I am thinking there has to be a more accurate way to do this beside taking a daily sample to the pool store. Plus I always feel like a cheap skate scince the pool store doesn't charge to run the samples and I usually don't buy any chemicals.

    Thanks
    Eric

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    Mod Squad zea3's Avatar
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    Re: Test kits and accuracy

    Hi welcome to TFP! If you use a FAS-DPD kit, then the only color comparisons are for the pH test. CH, TA, and Chlorine tests are read by counting the number of drops until a complete color change occurs. Computer based tests are not as accurate as you may think. They are just as prone to user error as any other testing method, and they must be re-calibrated on a regular basis to maintain accuracy. A home version of the equipment would be expensive. There are some home electronic test systems available but most of the reviews I have heard have not been good long term.

    Which test kit are you using now?
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    Re: Test kits and accuracy

    Computer based tests are not as accurate as you may think.
    Hi, Eric. Take Zea's words to the bank. Digital readouts are precise but often WILDLY inaccurate. Often, they use a test strip dipped into your sample and then read the colors from that strip. That is a very inaccurate way to test and, if you search through the forum, you will see practically hundreds of posts reporting just how poor those digital readouts are.

    Drops based kits, (whether yours or the pool stores) are still the most accurate (and repeatable) way to test your water and their precision is perfectly adequate for you to maintain crystal clear water.
    Dave S.
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    Re: Test kits and accuracy

    Often, the pool store computers simply guess colors from a test strip, and can be less accurate than painting a car with a chainsaw. The 10-decimal representation of a digital value which is a measure of an analog guess is still a guess.

    Performing your own testing will get you the most accurate and, more importantly, the most consistent results, because you have a far more vested interest in your pool. With all due respect to the professionals who create test kits and those who perform testing, having consistent repeatable results is more important than having accurate results, as one can compensate for accuracy. Doing the tests yourself the same way each time will be the biggest single factor of your pool maintenance results. The second biggest will be a good test kit.

    To accurately measure chlorine, the best test is a FAS-DPD test, which is a titration test and can be extremely precise. There are two test kits which have this test and are most recommended on this forum, the Taylor K-2006, and the TF-100. Of the two, most of us get the TF-100, as it is custom assembled from Taylor test reagents, include more of the most-often used reagents, and specifically include the tests we have determined that are most needed. As a disclaimer, the TF-100 is sold by our own Duraleigh via the TFTestkits Website. Either kit will do what you need.
    [center:1kpalu48]Helpful Links: Pool School | CYA/Chlorine Chart | Pool Calculator[/center:1kpalu48]

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    Re: Test kits and accuracy

    Just bite the bullet, go order a TF100 and a speedstir.

    pH is really the only color matching you have to do, and the acceptable range is pretty generous there. Is it pink, peach, or orange?

    The CYA test is also a fun one. I found it worthwhile to also buy the standard solution - a sample of known 50ppm CYA, and used that to test my skill. Turns out I was dead on, but it was cheap reassurance.

    The other tests are color changes. I suppose if you're color blind it could be a problem, but most people can tell green from pink, and pink from purple from blue.
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    Re: Test kits and accuracy

    Thanks for all the help guys. Looks like all the bells and whistles are not always better. zea3, right now I am just using the kit that the pool builder gave me when they came to do pool school; probably not the best out there. I guess I will go online and get the TF-100 and a speed stir. I assume a speed stir is a magnetic stirer like one used in a chem lab, correct? Thanks again, this will be my first quetion of many I am sure.

    Eric

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    Re: Test kits and accuracy

    I've noticed a couple of things about different test kits. TF-100 and the leslie complete DPD kit. The CYA test is higher in leslie kit versus TF-1000. It's basically the same regent but differnt examination tube and amount of water and regent. Difference is more than 10% like difference between 40 and 20 in a recent test. In both cases I've tried new and older regents and get consistent but different results between kits. Also I recenty purchased the speedstir and noticed the graduated cylinder given with speedsteer measures 10ML with only about 8.5ML of solution compared to cylinders given in regular TF-100 kit. Which one is right? Any help making since of this would be appreciated.

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    Re: Test kits and accuracy

    I do know, having compared both, that the Taylor 9198 cell is bang on when compared to a 25 mL Class-A volumetric flask.

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    Re: Test kits and accuracy

    Feeling that I must chime in to second, excepting probably the lab grade electronic testing devices that run $100,000 and up, drop based kits are the most accurate and precise testing kits out there. Most electronic ones that you find at pool stores are woefully lacking in the accuracy department and the results of these machines are much of the reason why we see confused and disgruntled pool owners show up here at TFP by the thousands each year, looking for the help that they couldn't quite get at their pool supply retailer.

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    Re: Test kits and accuracy

    I worked with somebody who swore by the Palin kits. Unfortunately the readings were not always on and IMO it took longer to test than it would with the drop based kits. Anybody else have experience with Palin??

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    Re: Test kits and accuracy

    No to highjack this thread, and it's kinda on topic as far as maintaining accuracy...

    I ran out of the R0871 (more is on the way from TF), and none of the local places sell Taylor replacements -- they only sell Pentair. Don't you need to stick with the same brand of reagents since some companies have different concentrations?
    7000 gallons, S8M500 Filter, IG beadcrete plaster, IntelliFlo VS

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    Re: Test kits and accuracy

    Quote Originally Posted by RAILhead
    No to highjack this thread, and it's kinda on topic as far as maintaining accuracy...

    I ran out of the R0871 (more is on the way from TF), and none of the local places sell Taylor replacements -- they only sell Pentair. Don't you need to stick with the same brand of reagents since some companies have different concentrations?
    Yep, gotta stick with the same brand. Around here, even if a dealer carries Taylor, they do not carry the R0871 or R0870
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    Re: Test kits and accuracy

    Quote Originally Posted by Buford
    Quote Originally Posted by RAILhead
    No to highjack this thread, and it's kinda on topic as far as maintaining accuracy...

    I ran out of the R0871 (more is on the way from TF), and none of the local places sell Taylor replacements -- they only sell Pentair. Don't you need to stick with the same brand of reagents since some companies have different concentrations?
    Yep, gotta stick with the same brand. Around here, even if a dealer carries Taylor, they do not carry the R0871 or R0870
    Thanks for the confirmation! My replacements are on their way from Dave, so I'll be up and testing again tomorrow -- and I now known when I need to reorder.
    7000 gallons, S8M500 Filter, IG beadcrete plaster, IntelliFlo VS

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